This disclosure relates to a shaft driving apparatus and method of operation. The disclosed shaft driving apparatus and method of operation are especially relevant to applications where a bearing supported shaft is oscillated a relatively small angular range. One example of a bearing supported shaft which is oscillated a relatively small angular range is a printing apparatus decision gate for directing a print media sheet along one of multiple paths.
With reference to FIGS. 10A and 10B, illustrated is a front and end view, respectively, of a conventional shaft driving apparatus 280 and associated load 288. The shaft driving apparatus 280 includes a controller 282, a motor 284, a shaft 286, a load 288, a coupler 302, a first bearing 306, a second bearing 308, and a rigid joint 304 which couples the load 288 and shaft 286. In operation, the controller 282 and/or motor 284 rotate the shaft 286 which rides on the bearings, 306 and 308, to rotate the rigid coupler 304 and load 288.
With regard to the wear of the bearings, eventually one or more of the ball bearings housed within the bearing structure will fail and require replacement. In addition, bearings housed within the motor will eventually need replacement. For applications of the shaft driving apparatus 280 which require complete rotations of the shaft 286, the bearings and all associated bearing balls housed within a particular bearing housing tend to wear at a relatively uniform rate. However, for applications of the shaft driving apparatus 280 which require repetitive incomplete rotations of the shaft where the shaft rotates from a first angular position to a second angular position less than a full rotation of the shaft, the associated bearing balls within a particular bearing housing tend to wear unevenly. With continued reference to FIG. 10B, illustrated is a conventional shaft driving apparatus 280 where the shaft 286 and load 288 do not rotate a full rotation of the shaft 286. The apparatus 280 rotates an angular motion range 312 less than a complete rotation.
Under the conditions where a shaft is rotated an angular motion range less than 360°, the complete bearing assemblies associated with the shaft fail due to the failure of one or more of the bearing balls housed within the ball bearing assembly.
This disclosure provides a shaft driving apparatus and method of operation to extend the life of bearings where the shaft is repetitively rotated an angular motion range less than 360°. This disclosure is especially suited to an oscillating decision gate and/or tamper arm as used in a printing apparatus. However, the disclosure is not limited to these applications.